Methods of lapping while heating one or more features, and related sliders, row bars, and systems

ABSTRACT

The present disclosure includes methods of lapping that include energizing one or more elements that are located proximal to a first magnetoresistive element in a transducer region and generate heat and cause the first magnetoresistive element to selectively expand in the lapping direction relative to one or more other magnetoresistive elements. The present disclosure also includes methods of lapping that use one or more thermal sensors located proximal to the first magnetoresistive element to help control lapping in the lapping direction. The present disclosure includes related lapping systems and sliders.

RELATED APPLICATION

This application is a divisional patent application of application Ser.No. 16/434,853 filed on Jun. 7, 2019, which in turn claims the benefitof commonly owned provisional Application having Ser. No. 62/686,433,filed on Jun. 18, 2018, wherein each of said patent applications areincorporated herein by reference in their entirety.

BACKGROUND

The present disclosure relates to systems and methods of lapping aslider and/or row bar of sliders that can ultimately be used in a harddisc drive for read/write operations.

SUMMARY

The present disclosure includes embodiments of a method of lapping a rowbar having a plurality of sliders, wherein the method comprises:

a) providing the row bar having a plurality of sliders, wherein at leastone slider comprises a transducer region comprising: at least a firstmagnetoresistive element and a second magnetoresistive element, whereinthe first magnetoresistive element has a first feature that has a firstdistance from a first target value in the lapping direction and thesecond magnetoresistive element has a second feature that has a seconddistance from a second target value in the lapping direction, whereinthe first distance minus the second distance is equal to a deltadistance; and

b) applying a current to an element in the transducer region to generateheat and cause at least the first magnetoresistive element to expand inthe lapping direction relative to the second magnetoresistive element,wherein the current is controlled to cause the first magnetoresistiveelement to expand in the lapping direction an amount equal to the deltadistance; and

c) lapping the row bar while applying the current.

The present disclosure also includes embodiments of a row bar having aplurality of sliders, wherein at least one slider comprises a transducerregion, wherein the transducer region comprises:

a) a magnetoresistive writer element;

b) a magnetoresistive reader element;

c) at least one electrical resistance heating element and/or at leastone thermal sensor located proximal to the magnetoresistive readerelement and/or the magnetoresistive writer element;

d) a first row of a plurality of electrical contact pads; and

e) a second row of a plurality of electrical contact pads, wherein thefirst row of electrical contact pads extends along a downtrack directionat a first position in a lapping direction, wherein the second row ofelectrical contact pads extends along the downtrack direction at asecond position in the lapping direction, wherein the at least oneelectrical resistance heating element and/or at least one thermal sensoris electrically coupled to at least one electrical contact pad in thesecond row, and wherein the at least one electrical contact pad in thesecond row is electrically coupled to at least one electrical contactpad in the first row.

The present disclosure also includes embodiments of a lapping systemcomprising:

a) a carrier structure;

b) the row bar of claim 16, wherein the row bar is removably mounted tothe carrier, wherein the carrier structure has a mechanical actuatorthat is configured to physically contact the row bar and actuate aslider in the lapping direction; and

c) a lapping plate having a lapping surface that is operable to rotateand contact the row bar for lapping the first magnetoresistive elementand the second magnetoresistive element.

The present disclosure also includes embodiments of a row bar having aplurality of sliders, wherein at least one slider comprises a transducerregion, wherein the transducer region comprises:

a) a magnetoresistive writer element;

b) a first electrical resistance heating element located proximal to themagnetoresistive writer element;

c) a magnetoresistive reader element;

d) a second electrical resistance heating element located proximal tothe magnetoresistive reader element; and

e) a third electrical resistance heating element located proximal to themagnetoresistive writer element or the magnetoresistive reader element.

The present disclosure also includes embodiments of a lapping systemcomprising:

a) a carrier structure;

b) the row bar of claim 18, wherein the row bar is removably mounted tothe carrier, wherein the carrier structure has a mechanical actuatorthat is configured to physically contact the row bar and actuate aslider in the lapping direction; and

c) a lapping plate having a lapping surface that is operable to rotateand contact the row bar for lapping the first magnetoresistive elementand the second magnetoresistive element.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1A shows a schematic, cross-section view of a portion of a sliderin a row bar that can be lapped according to the present disclosure;

FIG. 1B shows a schematic, cross-section view of a portion of themagnetoresistive writer element 105 shown in FIG. 1A;

FIG. 1C shows a schematic, cross-section view of a portion of themagnetoresistive reader element 110 shown in FIG. 1A;

FIG. 1D shows a schematic, cross-section view of the portion of theslider shown in FIG. 1A when the writer electrical resistive heater 125is energized;

FIG. 1E shows a schematic, bottom view of the portion of the slidershown in FIG. 1D;

FIG. 1F shows a schematic, cross-section view of the portion of theslider shown in FIG. 1D after the slider has been lapped;

FIG. 1G shows a schematic, cross-section view of the portion of theslider shown in FIG. 1E when the writer electrical resistive heater 125is no longer energized; and

FIG. 2 is a schematic, cross-section view of a portion of the slidershown in FIG. 1A that includes electrical contact pads.

DETAILED DESCRIPTION

A magnetic recording apparatus can be referred to as a hard disk drive(HDD) and includes a slider that flies above a disk by using air as alubricant (an “air bearing”). For example, a disk can be placed on aspindle motor that can rotate and a negative pressure air-lubricatedbearing slider can be attached at a suspension to correspond to themagnetic disk. The negative pressure air-lubricated bearing slider canbe moved by an actuator that pivots so that the slider moves to adesired position on a track of the disk. The disk used as a recordingmedium has a circular shape and different information can be recorded oneach track. In general, to obtain desired information, the slider movesin search of a corresponding track on the disk. The disk can have amagnetic layer that is susceptible to physical and/or chemical damage.To help mitigate such damage, such a disc often has a coating such asDiamond-like Carbon (DLC) as an overcoat to help protect the magneticlayer from physically and/or chemically induced damage.

A lapping tool is used for machining a surface of a row bar that can belater sliced into a plurality of individual sliders. The lapping toolcan have a rotating lapping plate defining a lapping surface which canhelp abrade the surface of a slider. If desired, a slurry can be appliedto the lapping surface to enhance the abrading action as the lappingsurface is rotated relative to a row bar containing a plurality of thesliders held in a pressing engagement against the lapping surface.Lapping a row bar of sliders permits multiple slider bodies to beprocessed together, which can advantageously be relatively simple,precise and/or cost-effective. Lapping can involve multiple lappingsteps such as rough lapping and final (kiss) lapping. At a desired pointin manufacturing, individual sliders can be sliced from the row bar andultimately used in a hard disk drive.

Rough Lapping can be considered a relatively coarse lapping procedureused to remove relatively more material as compared to kiss lapping. Forexample, rough lapping can remove up to 10 micrometers of material froma row bar in the lapping direction, or even up to 20 micrometers ofmaterial from a row bar in the lapping direction. A row bar can betilted at a specific position relative to the lapping plate to target aparticular element (e.g., reader or writer).

Kiss Lapping can be considered a fine lapping procedure and can be usedto remove fractions of material from a row bar as compared to roughlapping. For example, kiss lapping can remove 0.5 microns or less, oreven 0.1 microns or less of material from a row bar in the lappingdirection.

After rough lapping, but before kiss lapping, two or more electronicfeatures in the transducer region of a given slider may be at differentdistances from their target values in the lapping direction. Forexample, before kiss lapping, a magnetoresistive writer element (alsoreferred to as a “writer”) may be at a different distance from itstarget value as compared to a magnetoresistive reader element (alsoreferred to as a “reader”), thereby creating a delta distance (alsoreferred to as a reader/writer delta). Lapping to each target value of awriter and reader during kiss lapping can be difficult when areader/writer delta is present.

According to the present disclosure, a heat source in the transducerregion of a slider can be used to selectively expand an electronicfeature (e.g., a writer) relative to another feature (e.g., a reader)within a given slider so that the expanded portion can be removed,thereby reducing or eliminating the delta distance. For example, awriter could be expanded an amount in the lapping direction equal to thereader/writer delta so that that amount could be removed via lapping,thereby removing the reader/writer delta.

The present disclosure can be applied to a variety of slider heads suchas perpendicular magnetoresistive (PMR) heads, head-assistedmagnetoresistive (HAMR) heads, and the like. In some embodiments, thepresent disclosure can be especially useful with respect to PMR headsbecause the accuracy of the write pole width can be very desirable,especially as the write pole width is reduced and the flare angle isincreased.

Embodiments of the present disclosure can include a row bar having aplurality of sliders. At least one slider includes a transducer region.The transducer region includes at least a first magnetoresistive elementand a second magnetoresistive element. The first magnetoresistiveelement has a first feature that has a first distance from a firsttarget value in the lapping direction. The second magnetoresistiveelement has a second feature that has a second distance from a secondtarget value in the lapping direction. The first distance minus thesecond distance is equal to a delta distance. In some embodiments, asimilar relationship among every first magnetoresistive element andsecond magnetoresistive element is present in every slider in the rowbar. That is, every slider in a row bar includes at least a firstmagnetoresistive element and a second magnetoresistive element. Thefirst magnetoresistive element in each slider has a first feature thatis a first distance from a first target value in the lapping direction.The second magnetoresistive element in each slider has a second featurethat is a second distance from a second target value in the lappingdirection. And the first distance minus the second distance is equal toa delta distance. The delta distance may be the same or different amongindividual sliders.

In more detail, for illustration purposes, an embodiment according tothe present disclosure is described with respect to FIGS. 1A-1G wherethe first magnetoresistive element is a magnetoresistive writer element(writer) and the second magnetoresistive element is a magnetoresistivereader element (reader).

As used herein, the direction along x-axis (into the page of FIG. 1A) isreferred to as the cross-track axis. The direction along the z-axis isreferred to herein as the down-track axis, with reference to trailingedge 156. The direction along the y-axis is referred herein as thelapping direction (direction of material removal) or the reader stripeheight direction and writer break-point direction.

As shown in FIG. 1A, one slider 111 of a plurality of sliders in row bar100 is illustrated. Slider 111 includes a transducer region 101 havingat least a magnetoresistive writer element 105 and a magnetoresistivereader element 110. In some embodiments, a row bar according to thepresent disclosure can include at least 30 sliders, at least 60 sliders,or even at least 70 sliders. A slider according to the presentdisclosure can be mostly made out of ceramic material. As shown in FIG.1A slider 111 includes an “AlTiC break” 150. The area 151 to the rightof break 150, the bulk of the material is alumina titanium-carbide (alsoreferred to as AlTiC). The area 152 to the left of break 150, the bulkof the material, with the exception of many of the features in thetransducer region 101, is alumina. Elements such as magnetoresistivewriter element 105 are made of magnetic materials such cobalt-iron(CoFe), nickel-iron (NiFe), and the like.

As shown in FIG. 1B, the magnetoresistive writer element 105 has a writepole 106 as a first feature that has a first distance 108 from a writerbreak point target position 109 as a first target value in the lappingdirection. The writer break point distance 107 coincides with the writerbreak point target position 109 at the air bearing surface 162 aftermaterial is removed in the lapping direction by an amount represented byfirst distance 108.

As shown in FIG. 1C, the magnetoresistive reader element 110 has areader stripe height 113 as a second feature that has a second distance112 from a reader stripe height target position 114 as a second targetvalue in the lapping direction. The reader stripe height 113 coincideswith the reader stripe height target position 114 at the air bearingsurface 162 after material is removed in the lapping direction by anamount represented by second distance 112.

Referring back FIG. 1A, as can be seen, there is a difference (delta)120 between first distance 108 and second distance 112. That is, thedistance 108 of the magnetoresistive writer element 105 from its writerbreak point target position 109 is different than the distance 112 ofthe magnetoresistive reader element 110 from its reader stripe heighttarget position 114, thereby creating delta distance 120.

In some embodiments, the delta distance 120 is 50 nanometers or less.For example, delta distance 120 can be in the range from 0.1 nanometersto 40 nanometers, from 0.5 nanometers to 40 nanometers, or from 0.1nanometers to 10 nanometers.

As explained above, according to the present disclosure, a heat sourcein the transducer region of a slider can be used to selectively expandan electronic feature (e.g., a writer) relative to another feature(e.g., a reader) within a given slider so that the expanded portion canbe removed, thereby reducing or eliminating the delta distance 120.

Heat can be generated from a variety of electrical elements present in atransducer region of a slider. In some embodiments, the electricalelement in the transducer region can be chosen from an electricalresistive heater, writer coils of a magnetoresistive write element, alaser/near field transducer (on-wafer laser), and combinations thereof.

As shown in FIG. 1 , examples of electrical resistive heaters includeone or more of writer electrical resistive heater 125 and readerelectrical resistive heater 126. Writer electrical resistive heater 125is located proximal to magnetoresistive writer element 105 and readerelectrical resistive heater 126 is located proximal to magnetoresistivereader element 110. Writer electrical resistive heater 125 and/or readerelectrical resistive heater 126 are examples of electrical resistiveheaters that can be used during lapping according to present disclosureand during operation of a hard disc drive to adjust the distance betweenthe writer and/or reader, respectively, and an underlying rotating disc.

In some embodiments, one or more optional electrical resistive heaterscan be included that are dedicated to lapping operations. The one ormore optional electrical resistive heaters can be located proximal tothe feature that they are intended to selectively expand in the lappingdirection. As shown in FIG. 1 , the transducer region 101 includes anoptional electrical resistive heater 128 that is also located proximalto magnetoresistive writer element 105. In use during lapping, asdescribed below, the optional electrical resistance heating element 128can be energized during lapping to cause the magnetoresistive writerelement 105 to selectively expand relative to the magnetoresistivereader element 110 by an amount equal to delta distance 120, while theelectrical resistance element 125 is not energized during lapping. Inuse during hard disc drive operation, the optional electrical resistanceheating element 128 is not energized, but the electrical resistanceelement 125 can be energized to adjust the distance between themagnetoresistive writer element 105 and an underlying rotating disc (notshown).

Electrical resistive heaters (e.g., 125, 126, and 128) can be placedproximal to a magnetoresistive element so that it causes themagnetoresistive element to thermally expand in the “y” directionrelative to another magnetoresistive element in the slider by a desiredamount. For example, if writer electrical resistive heater 125 isenergized to generate heat, it can cause the magnetoresistive writerelement 105 to expand a first distance in the “y” direction. Further,when the writer electrical resistive heater 125 is energized to generateheat, it can also cause the magnetoresistive reader element 110 toexpand a second distance in the “y” direction depending on the locationof the writer electrical resistive heater 125 in the downtrack “z”direction. The ratio of the first distance to the second distance can bereferred to as “gamma.” In some embodiments in can be desirable tolocate an electrical resistive heater (e.g., 125) proximal to itsassociated magnetoresistive element (e.g., 105) so that “gamma” isrelatively high so that, e.g., writer electrical resistive heater 125causes little to no expansion of the magnetoresistive reader element 110in the “y” direction. In some embodiments, an electrical resistiveheater (e.g., writer electrical resistive heater 125) is proximallylocated to its associated magnetoresistive element (e.g.,magnetoresistive writer element 105) so that the heater is from 0.5 to 5micrometers in the downtrack direction from the magnetoresistiveelement. In some embodiments, energizing an on-wafer-laser can be adesirable element to energize during lapping because it can relativelylocalize the heat that is generated thereby producing a relatively highand desirable “gamma.”

In some embodiments, an electrical resistive heater can be located abovethe air bearing surface in the lapping direction “y” by a distance inthe range from 1 to 10 micrometers.

In some embodiments, two or more sliders 111 in the row bar 100 havedelta distances 120. In some embodiments, all sliders 111 in the row bar100 have delta distances 120. Two or more delta distances 120 within arow bar 100 can have delta distances that are different from each other.In such cases, as described below, the present disclosure can apply anappropriate heat source to each individual slider to create acorresponding expansion by the appropriate delta distance in the lappingdirection to remove the expanded material during lapping, therebyreducing or eliminating the delta distance among features within a givenslider.

Embodiments of the present disclosure include applying a current to anelement in the transducer region to generate heat and cause at least afirst magnetoresistive element to expand in the lapping directionrelative to at least a second magnetoresistive element. The current canbe controlled to cause the first magnetoresistive element to heat up andexpand in the lapping direction by an amount equal to the deltadistance. The coefficient of thermal expansion of each of the differentareas or elements within the area being heated can be taken into accountwhen determining how much current to apply to the element that generatesheat.

An example of applying current to an element to cause an area to heat upand selectively expand during lapping is described with respect to FIGS.1D-1G. The slider in FIG. 1A represents a slider 111 that has beenthrough rough lapping. FIGS. 1D-1G represent various points in a kisslapping process. Referring to FIG. 1D, a pre-determined current isapplied to an element 125 in the transducer region 101 to generate heatand cause at least the first magnetoresistive element 105 to expand inthe lapping direction relative to the second magnetoresistive element110. The current can be adjusted and controlled to cause the firstmagnetoresistive element 105 to expand in the lapping direction anamount equal to the delta distance 132, which corresponds to deltadistance 120 in FIG. 1A. As shown in FIG. 1D, delta distance 132 is thedistance between reference line 130 and reference line 131. Referenceline 130 is coplanar with air bearing surface 162. The amount of currentto cause protrusion 132 can be determined from the heat generated fromthe element due to resistance heating and the coefficient of thermalexpansion of the area that is heated. For example, referring to FIGS. 1Dand 1E, an amount of current is applied to heater 125 to cause the area117 to expand in the lapping direction “y” toward lapping plate 160. Thecoefficient of thermal expansion of the area 117 is taken into accountto determine how much current to apply to heater 125 to expandmagnetoresistive writer element 105 by a distance 132.

The row bar 111 can be caused to contact the rotating surface 161 oflapping plate 160 so that the expanded portion of the slider 111 can beremoved, as shown in FIG. 1F, while applying the current. As also shownin FIG. 1F, the slider 111 has been lapped to planarize slider 111 sothat the ABS 162 corresponds to the reader stripe height target position114 of the magnetoresistive reader element 110. As shown in FIG. 1G,when the current is stopped so no heat is generated via heater 125, thearea 117 cools down and recedes so that magnetoresistive writer element105 recedes in the lapping direction “y” by a distance equal to deltadistance 120. Thus, the air bearing surface 162 at the magnetoresistivewriter element 105 now coincides with the writer break point targetposition 109. Accordingly, a degree of freedom can be introduced intothe lapping process (e.g., kiss lapping process) by heating an elementsuch as electrical resistance element 125. In some embodiments, acurrent can be applied to every slider in a row bar to cause themagnetoresistive writer element 105 in each slider 111 to expand in thelapping direction by an amount corresponding to the delta 120 of eachslider 111. Thus, for every electrical resistance element 125 usedduring lapping as described above the same number of degrees of freedomcan be introduced for that row bar 100. In some embodiments, a lappingsystem can connect a wire to the writer electrical resistive heater 125on every head of every slider 111. Current can flow down one slider andup an adjacent slider, and any remaining current imbalance can behandled by a ground pad connection on first and last (dummy) sliders onevery row bar.

In some embodiments, the one or more elements in each slider that areselected to electrically generate heat as described herein can be theonly elements in the slider that are energized with current duringlapping. For example, with respect to FIG. 1A, the writer electricalresistive heater 125 can be the only element in slider 111 that isenergized with current during lapping while current is not applied to,e.g., the magnetoresistive writer element 105 and the magnetoresistivereader element 110 during lapping. As another example, the writerelectrical resistive heater 125 and/or the writer coil ofmagnetoresistive writer element 105 can be energized with current togenerate heat while current is not applied to, e.g., themagnetoresistive reader element 110 during lapping.

As described above, one or more sliders 111 in a row bar 100 can have adelta distance 120 that is different from a delta distance in one ormore other sliders 111 in the row bar. As one example, each slider 111in a row bar 100 could have a delta distance 120 that is different fromthe delta distance 120 in every other slider in the row bar 100. Becausethe delta distance 120 can vary among sliders in a row bar, the currentthat is applied to each individual heat generating element in eachslider 111 (e.g., writer electrical resistive heater 125) can bedifferent from the current applied to every other individual heatgenerating element in each corresponding slider 111 (e.g., writerelectrical resistive heater 125).

In some embodiments, controlling kiss lapping to writer break pointtarget position 109 can be performed with writer electrical resistiveheater 125 and controlling kiss lapping to reader stripe height targetposition 114 can simultaneously be performed with an actuator arm of amounting carrier. Examples of lapping carriers are described in U.S.Pat. No. 9,776,299 (Herendeen) and U.S. Pub. No. 2015/0258655 (Koon etal.), wherein the entireties of said patent documents are incorporatedherein by reference. In some embodiments, controlling lapping to writerbreak point target position 109 and reader stripe height target position114 can be performed in this manner for each slider 111 of a row bar.This corresponds to two degrees of freedom of lapping control for eachslider 111. For example, if a row bar has 68 sliders, then using awriter electrical resistive heater and carrier actuator for themagnetoresistive writer element 105 and the magnetoresistive readerelement 110, respectively, of each slider as described herein canprovide at least 136 degrees of freedom for lapping control.

In some embodiments, before kiss lapping as described herein withrespect to FIGS. 1A-1G, a magnetoresistive element such asmagnetoresistive writer element 105 can be intentionally underlappedfrom the writer break point target position 109. In some embodiments,one or more magnetoresistive elements can be underlapped in the lappingdirection by a distance from 0.5 to 10 nanometers. This can facilitateusing a heat source according to the present disclosure to causerelative expansion among magnetoresistive elements and avoid overlappingthe magnetoresistive element that is underlapped.

A variety of alternatives can be configured according to the presentdisclosure. For example, the reader electrical resistive heater 126could be energized during lapping instead of writer electrical resistiveheater 125. This way, the magnetoresistive reader element 110 could becaused to expand due to the heat generated by reader electricalresistive heater 126. Simultaneously and in conjunction, a carrieractuator could be used to physically actuate the slider 111 and controlthe writer break point target position 109 of magnetoresistive writerelement 105.

In some embodiments, one or more electronic lapping guides (ELGs) can beused during lapping. An ELG has an electrical resistance that can changeas conditions change. For example, the electrical resistance of an ELGcan increase as ELG material is removed during a lapping process andthus may be used to monitor lapping of the air bearing surface 162during slider 111 manufacturing. Accordingly, an ELG may be formed in aslider and the ELG resistance may be monitored during lapping. Theresistance of an ELG can be correlated to material removed from anelement that the ELG is associated with such as magnetoresistive writerelement 105, magnetoresistive reader element 110, and/or a near-fieldtransducer (not shown). Thus, the ELG can be used to target a desireddimension of the magnetoresistive writer element 105, themagnetoresistive reader element 110, and/or a near-field transducer. Forexample, an ELG can be used during lapping to target a height value forthe magnetoresistive reader element 110 (e.g. reader stripe heighttarget position 114) and another ELG can be used during lapping totarget a height value for the magnetoresistive writer element 105 (e.g.,writer break point target position 109). ELGs are also described in U.S.patent documents 7,551,406 (Thomas et al.), U.S. Pat. No. 7,643,250(Araki et al.), U.S. Pat. No. 8,165,709 (Rudy), 2006/0168798 (Naka), and2010/0208391 (Gokemeijer), wherein there entireties of said patentdocuments are incorporated herein by reference.

As shown in FIG. 1E, slider 111 includes a writer ELG 115 and a readerELG 116. Writer ELG 115 and reader ELG can each be located hundreds ofmicrons away in the cross-track direction “x” from magnetoresistivewriter element 105 and magnetoresistive reader element 110,respectively. During lapping, if writer electrical resistive heater 125is used as described herein to expand slider 111 in the area 117 (“heatbubble”), then the writer ELG 115 can likewise be hundreds of micronsoutside of area 117. If the writer ELG 115 is located outside the area117, then the writer ELG 115 may not provide the intended metrology withrespect to magnetoresistive writer element 105 while magnetoresistivewriter element 105 is expanding as shown in FIG. 1D. In someembodiments, one or thermal sensors can be located proximal (e.g.,within area 117) to a given element being expanded (e.g.,magnetoresistive writer element 105). Advantageously, a thermal sensorcan provide desirable metrology information with respect to an elementduring lapping while the element is expanded due to heating. Forexample, a thermal sensor 127 can be located proximal tomagnetoresistive writer element 105 within area 117. In someembodiments, a thermal sensor can be located within 0.5 to 5 micrometersin the downtrack “z” direction of its associated magnetoresistiveelement. A the thermal sensor can be located above the final air bearingsurface in the lapping direction such that material is not removed fromthe thermal sensor during lapping as is the case with its associatedmagnetoresistive element. In some embodiments, a thermal sensor can belocated above the air bearing surface in the lapping direction “y” by adistance in the range from 0.1 to 1 micrometers.

During lapping, while current is applied to writer electrical resistiveheater 125 and heating area 117, the resistance of thermal sensor 127can be measured. Temperature can be inferred from the measuredresistance of thermal sensor 127. Then, the inferred temperature can beused to calculate the corresponding protrusion of magnetoresistivewriter element 105 from a model that correlates temperature toprotrusion of magnetoresistive writer element 105.

A non-limiting example of correlating temperature to protrusion ofmagnetoresistive writer element 105 is described herein below. A thermalsensor such as sensor 127 can be a thin sheet of resistive metal thatcan be used determine resistance vs temperature for the thermal sensor127 either empirically or using a look-up table. An empirical approachcan include raising and/or lowering the ambient temperature andmeasuring the resistance change of the sensor 127 in a row bar 100 as afunction of temperature. Using a look-up table can include obtainingliterature values from a look-up table for resistance change vstemperature for the material(s) used in this thermal sensor 127.

Also, a model for heater current or power vs temperature can be used.This can involve electrically connecting to a heater in a slider (e.g.,a reader heater, a writer heater, or a dedicated lapping heater) andelectrically connecting to a thermal sensor (e.g., sensor 127) in theslider. Next, the current or power delivered to the heater can be variedand the resistance of the thermal sensor 127 measured. Finally, theheater current or power can be plotted versus the resistance of thermalsensor 127. It is noted that this calibration method can be done whilenot lapping, because lapping may remove material from the thermal sensorand cause resistance to change. Also, calibration can be done with a rowbar in contact with a static (non-rotating) lapping plate or without arow bar in contact with a lapping plate.

Finally, correlating temperature to protrusion of magnetoresistivewriter element 105 can include a model for temperature vs protrusion ofa writer or reader. Commercially available software packages areavailable like COMSOL Multiphysics® software that can be used to modelthe protrusion profiles of a writer or reader while an electrical heateris used at different power settings. Empirical modeling can be performedby electrically connecting to a heater, lapping bars under under a rangeof heater currents/powers, and then measuring the height profiles for areader and a writer protrusion using either an atomic force microscopeor with an optical profilometer

One non-limiting example of a thermal sensor 127 is referred to as adual-ended temperature coefficient of resistance sensor (DETCR). Anexample of a DETCR is described in U.S. Pat. No. 8,638,349 (Liu et al.),wherein the entirety of said patent document is incorporated herein byreference. Another non-limiting example of a thermal sensor 127 includesa thermal asperity detector (TAD). An example of a TAD is described inU.S. Pub. No. 2003/0065992 (Yang), wherein the entirety of said patentdocument is incorporated herein by reference.

In some embodiments, the temperature of a row bar 111 canunintentionally fluctuate due to one or more factors such as frictionalheating due to lapping, the temperature of the surrounding environment.Such fluctuations may cause the elements that are heated to expand(e.g., e.g., the magnetoresistive writer element 105 and themagnetoresistive reader element 110) more or less than intended. Also,such fluctuations in temperature can increase or decrease the resistancedetected in an ELG, which can indicate an incorrect amount of materialthat is lapped away from the ELG and corresponding element. A lappingplate having a temperature control system can help control thetemperature of the a row bar in physical contact with the lapping placeso as to reduce or substantially eliminate such temperaturefluctuations. An example of such a temperature control system isdescribed in patent application titled “A LAPPING SYSTEM THAT INCLUDES ALAPPING PLATE TEMPERATURE CONTROL SYSTEM, AND RELATED METHODS” byHabermas et al. having application No. 62/686,417 filed on Jun. 18,2018, wherein the entirety of said patent application is incorporatedherein by reference.

In order to electronically access slider elements (e.g.,magnetoresistive writer element 105, etc.), a slider can include aplurality of electrical contact pads that may be electrically connectedto the slider elements. FIG. 2 is a schematic that shows the trailingedge face 157 of slider 111. The contact pads illustrated are present onthe trailing edge face. FIG. 2 also includes an electrical wiringdiagram showing how the contact pads are electrically connected todevices such as ELGs, writer heater, DETCR. and the like. As shown inFIG. 2 , slider 111 includes a first row 205 of electrical contact padsalong the cross track axis “x” and a second row 220 of electricalcontact pads along the cross track axis “x”. The first row 205 ofcontact pads include a ground contact pad 208 and can be electricallyconnected to features used during head-gimbal assembly (HGA) operationin a hard disk drive (HDD). The second row 220 of electrical contactpads can be dedicated for use of features used during lapping accordingto the present disclosure. That way, electrical connections can be madeto the second row 220 of electrical contact pads and then after lappingis done, the second row 220 of electrical contact pads can just be leftunused, thereby leaving the first row 205 of electrical contact pads inrelatively good condition. For example, the first row 205 of electricalcontact pads can avoid having undue scratching or any remnants of wirebonds from the lapping process.

In more detail, with reference to the slider 111 illustrated in FIGS.1A-1G, electrical contact pads 206 and 207 can be electrically connectedto magnetoresistive writer element 105 and electrical contact pads 211and 212 can be electrically connected to magnetoresistive reader element110. Reader electrical resistive heater 126 can be electricallyconnected to electrical contact pad 213.

With respect to the slider 111 elements used during lapping as describedherein, writer ELG 115 can be electrically connected to electricalcontact pads 222 and 223 and reader ELG 116 can be electricallyconnected to electrical contact pads 221 and 222. Advantageously, writerELG 115 and reader ELG 116 can share a common electrical contact pad 222to save space in the second row 220 of electrical contact pads.

Also, thermal sensor 127 (e.g., DETCR) can be electrically connected toelectrical contact pads 225 and 226 in the second row 220, which can beelectrically connected to electrical contact pads 209 and 210,respectively, in the first row 205. Finally, writer electrical resistiveheater 125 can be electrically connected to electrical contact pad 224in the second row 220 and electrical contact pad 214 in the first row205. This way, electrical connections can be made to electrical contactpads in the second row 220 for lapping purposes, thereby avoiding unduescratching and/or remnants of wire bonds on electrical contact pads inthe first row 205.

Electrical contact pads can be made out a variety of conductivematerials such as gold and the like. Elements can be electricallyconnected to contact pads via bonding, soldering, or other electricalconnection. For example, gold wire can be used to electrically connect acontact pad to an element.

What is claimed is:
 1. A row bar having a plurality of sliders, whereinat least one slider comprises a transducer region, wherein thetransducer region comprises: at least a first magnetoresistive element,wherein the first magnetoresistive element has a first feature that hasa first distance from a first target value in a lapping direction; afirst electrical resistance heating element located proximal to thefirst magnetoresistive element; at least a second magnetoresistiveelement, wherein the second magnetoresistive element has a secondfeature that has a second distance from a second target value in thelapping direction, wherein the first distance minus the second distanceis equal to a delta distance; a second electrical resistance heatingelement located proximal to the second magnetoresistive element; and athird electrical resistance heating element located proximal to thefirst magnetoresistive element or the second magnetoresistive element.2. The row bar of claim 1, wherein the third electrical resistanceheating element is located proximal to the first magnetoresistiveelement, wherein the first magnetoresistive element is amagnetoresistive writer element.
 3. A lapping system comprising: a) acarrier structure; b) the row bar of claim 1, wherein the row bar isremovably mounted to the carrier structure, wherein the carrierstructure has a mechanical actuator that is configured to physicallycontact the row bar and actuate a slider in the lapping direction; andc) a lapping plate having a lapping surface that is operable to rotateand contact the row bar for lapping the first magnetoresistive elementand the second magnetoresistive element.
 4. The system of claim 3,wherein the system comprises a controller having program instructionscomprising: applying a current to the third electrical resistanceheating element in the transducer region to generate heat and cause atleast the first magnetoresistive element to expand in the lappingdirection relative to the second magnetoresistive element, wherein thecurrent is controlled to cause the first magnetoresistive element toexpand in the lapping direction an amount equal to the delta distance;and lapping the row bar while applying the current.
 5. The system ofclaim 4, wherein the delta distance is in a range from 0.5 to 50nanometers.
 6. The system of claim 4, wherein every slider in the rowbar comprises: at least a first magnetoresistive element and a secondmagnetoresistive element, wherein the first magnetoresistive element ineach slider has a first feature that is a first distance from a firsttarget value in the lapping direction, a first electrical resistanceheating element located proximal to the first magnetoresistive element,wherein the second magnetoresistive element in each slider has a secondfeature that is a second distance from a second target value in thelapping direction, wherein the first distance minus the second distanceis equal to a delta distance; a second electrical resistance heatingelement located proximal to the second magnetoresistive element; and athird electrical resistance heating element located proximal to thefirst magnetoresistive element or the second magnetoresistive element,wherein the program instructions comprise applying current to the thirdelectrical resistance heating element in the transducer region of eachslider in the row bar to generate heat and cause at least the firstmagnetoresistive element in each slider to expand in the lappingdirection relative to the second magnetoresistive element in eachcorresponding slider, wherein the current is controlled to cause thefirst magnetoresistive element in each slider to expand in the lappingdirection an amount equal to the delta distance in the correspondingslider.
 7. The system of claim 6, wherein at least two sliders in therow bar have different delta distances.
 8. The system of claim 7,wherein applying current to the third electrical resistance heatingelement in one slider is different than the current applied to the thirdelectrical resistance heating element for at least one other slider. 9.The system of claim 4, wherein the program instructions compriseenergizing the first electrical resistance heating element duringlapping and not energizing the second electrical resistance heatingelement during lapping.
 10. The system of claim 4, wherein the firstmagnetoresistive element is a magnetoresistive writer element and thefirst feature is a writer break point, and wherein the secondmagnetoresistive element is a magnetoresistive reader element and thesecond feature is a reader stripe height.
 11. The system of claim 4,wherein the transducer region further comprises at least one thermalsensor located proximal to the first magnetoresistive element andwherein the program instructions further comprise: measuring aresistance of the thermal sensor while applying the current to the thirdelectrical resistance heating element; comparing the measured resistanceof the thermal sensor to the applied current; and determining the firstdistance from target value of the first feature of the firstmagnetoresistive element.
 12. The system of claim 4, wherein the carrierstructure comprises a mechanical member for each slider, wherein eachmechanical member is configured to physically contact the row bar andactuate a corresponding slider in a lapping direction while applying thecurrent and lapping the row bar.
 13. The system of claim 4, wherein theprogram instructions comprise not applying current to the first andsecond magnetoresistive elements during the lapping.
 14. The system ofclaim 4, wherein the at least one slider further comprises a first rowof a plurality of electrical contact pads and a second row of aplurality of electrical contact pads, wherein the first row ofelectrical contact pads extends along a crosstrack direction at a firstposition in the lapping direction, wherein the second row of electricalcontact pads extends along the crosstrack direction at a second positionin the lapping direction, wherein the first electrical resistanceheating element is electrically coupled to at least one electricalcontact pad in the second row.